Covered stents with degradable barbs

ABSTRACT

The present invention is directed at a removable stent for providing reinforcement to a selected region of a selected body lumen including a resilient cylindrical layer, including at least one bioresorbable extrusion exterior from the resilient cylindrical layer for resisting migration of the removable stent when the removable stent is positioned in the selected region of the selected body lumen. The present invention also includes a temporary implantable endoprosthesis which includes a tubular, radially compressible and axially flexible structure, including at least one bioresorbable extrusion exterior from the resilient cylindrical layer for resisting migration of the removable stent when the removable stent is positioned in the selected region of the selected body lumen.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to an application entitled“Disintegrating Stent and Method of Making Same,” Ser. No. 09/592,413,by Jonathan Stinson, filed Jun. 13, 2000, the entire contents of whichis hereby incorporated by reference.

BACKGROUND

[0002] 1. Field of the Invention

[0003] The present invention relates generally to implantable medicalprostheses which incorporate an anchoring mechanism to reduce oreliminate migration of the prostheses.

[0004] 2. Description of Related Art

[0005] Medical prostheses frequently referred to as stents are wellknown and commercially available. These devices are used within bodyvessels of humans for a variety of medical applications. Examplesinclude intravascular stents for treating stenoses, stents formaintaining openings in the urinary biliary, tracheobronchial,esophageal, and renal tracts, and vena cava filters. Stents may also beused by physicians for malignant tumors. Benign tumors are seldomstented with metal platforms.

[0006] Typically, a stent is delivered into position at a treatment sitein a compressed state using a delivery device. After the stent ispositioned at the treatment site, the delivery device is actuated torelease the stent. Following release of the stent, self-expanding stentsare allowed to self-expand within the body vessel. Alternatively, aballoon may be used to expand other types of stents. This expansion ofthe stent in the body vessel helps to retain the stent in place andprevent movement or migration of the stent. Stents are typicallycomposed of stent filaments.

[0007] Stents may be categorized as permanent, removable orbioresorbable. Permanent stents are retained in place and incorporatedinto the vessel wall. Removable stents are removed from the body vesselwhen the stent is no longer needed. A bioresorbable stent may becomposed of, or include, biogradable material or bioresorbable materialwhich is broken down by the body and absorbed or passed from the bodywhen it is no longer needed.

[0008] Commonly used materials for known stent filaments includeElgiloy® and Phynox® metal spring alloys. Other metallic materials thatmay be used for stents filaments are 316 stainless steel, MP35N alloyand superelastic Nitinol nickel-titanium. Another stent, available fromSchneider (USA) Inc. of Minneapolis, Minn., has a radiopaque cladcomposite structure such as shown in U.S. Pat. No. 5,630,840 to Mayer.Stents can also be made of a titanium alloy as described in U.S. Pat.No. 5,888,201.

[0009] Bioabsorbable implantable endoprostheses such as stents,stent-grafts, grafts, filters, occlusive devices, and valves may be madeof poly(alpha-hydroxy acid) such as poly-L-lactide (PLLA),poly-D-lactide (PDLA), polyglycolide (PGA), polydioxanone,polycaprolactone, polygluconate, polylactic acid-polyethylene oxidecopolymers, modified cellulose, collagen, poly(hydroxybutyrate),polyanhydride, polyphosphoester, poly(aminoacides), or relatedcoploymers materials, each of which have a characteristic degradationrate in the body. For example, PGA and polydioxanone are relativelyfast-bioabsorbing materials (weeks to months) and PLA andpolycaprolactone are a relatively slow-bioabsorbing material (months toyears).

[0010] Stents may also be covered with various materials to encourage orinhibit tissue attachment to the stent. Covered stents are gaining,favor for biliary applications because they more effectively inhibittissue attachment, intrusion, and constriction of the tract than barestents. For example, polytetrafluoroethylene (PTFE) covered stents aredesirable for removable stents because tissue attachment or in-growth isreduced in comparison to bare stent or a stent covered with textile(polyester) material. Laminated ePTFE may also be used to cover stents.

[0011] As stents are covered with material to aid in their removal,stent migration from the treatment site increases. There remains acontinuing need for covered stents which include characteristics tomaintain the stent in position at the treatment site. For example,stents covered with ePTFE, such as Precedent, are easily removed after agiven time period, such as six months, but may not provide sufficientfixation to prevent the risk of migration during the six month period.

SUMMARY

[0012] The present invention relates to a removable stent for providingreinforcement to a selected region of a selected body lumen including aresilient cylindrical layer. The improvement to the stent is theinclusion of at least one bioresorbably extrusion exterior from theresilient cylindrical layer for resisting migration of the stent whenthe stent is positioned in the selected region of the selected bodylumen.

[0013] Another embodiment of the present invention includes at least onebioresorbable extrusion exterior from a resilient cylindrical layer of atemporary implantable endoprosthesis. The bioresorbable extrusionexterior to the resilient cylindrical layer resists migration of thestent when the stent is positioned in a selected region of a selectedbody lumen.

[0014] The present invention also includes a method of reducingmigration of a removable stent which includes the steps of constructinga removable stent including a resilient cylindrical layer and placing atleast one bioresorbable extrusion exterior from the resilientcylindrical layer on the stent. The removable stent is then positionedand expanded within a body lumen. Migration of the stent is resisted bythe interaction between the at least one biosorbable extrusion and thebody lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] We first briefly described the drawings.

[0016]FIG. 1 is an isometric view of an example of a braided nitinolstent, comprised of 0.25 mm single filament strands that incorporatesbioresorbable extrusions of the present invention;

[0017]FIG. 2 is a simplified representation of a braided tubular stentof the type illustrated in FIG. 1 incorporating bioresorbable extrusionsof the present invention;

[0018]FIG. 3 illustrates another stent incorporating anotherbioresorbable extrusion of the present invention;

[0019]FIG. 4 is an isometric view of an example of a metal spring alloystent comprised of a single helical coil that a bioresorbable extrusionof the present invention may be used in connection with;

[0020]FIG. 5 is an isometric view of a rolled film or sheet-typebioabsorbable stent that may be used in connection with thebioresorbable extrusion of the present invention;

[0021]FIG. 6 is an isometric view of a solid extruded or moldedtube-type stent that may be used in connection with the bioresorbableextrusion of the present invention;

[0022]FIG. 7 is an isometric view of a knitted or woven polymerfilament-type stent that may be used in connection with bioresorbableextrusion of the present invention;

[0023]FIG. 8 is a side view of a delivery device with the sent shown inFIG. 1 loaded thereon;

[0024]FIG. 9 is a detailed view of the portion of the delivery deviceencircled at “FIG. 9” in FIG. 8;

[0025]FIG. 10 is a detailed view of the portion of the delivery deviceencircled at “FIG. 10” in FIG. 8;

[0026] FIGS. 11-14 are partial cross-sectional side views of the distalportion of the delivery device and stent shown in FIG. 8 at variousstages during a stent deployment operation in a body vessel; and

[0027]FIG. 15 is a side view of a pusher-type delivery device.

DETAILED DESCRIPTION

[0028] The present invention improves the fixation characteristics ofremovable stents by incorporating bioresorbable or bioabsorbable barbsonto the removable stent or a covered stent to anchor the stent duringthe service life of the stent.

[0029] An implantable prosthesis or stent 101 according to a preferredembodiment of the present invention is illustrated generally in FIGS. 1through 3. Each of these figures includes a removable stent body withbioresorbable exterior extrusions added which, when placed in a bodylumen, resist migration of the stent. FIG. 4 shows an alternativeembodiment of the invention according to which the removable stent iscomprised of a single helical coil of a metal spring alloy and thebioresorbable exterior extrusion is in the shape of a barb, angled toprevent migration of the stent once placed in a body lumen. FIG. 5 showsan alternative embodiment of the invention according to which theremovable stent is comprised of a rolled film or sheet and thebioresorbable exterior extrusions are positioned circumferentiallyaround the exterior of the stent. FIG. 6 shows an alternative embodimentof the invention according to which the removable stent is comprised ofa solid extruded or molded tube and the bioresorbable exteriorextrusions are triangular in shape to resist migration of the stent inany direction. FIG. 7 shows an alternative embodiment of the inventionaccording to which the removable stent is comprised of knitted or wovenmetal filaments and the bioresorbable exterior extrusions are in theshape of barbs curved towards the ends of the stent. Removable stentbodies of the type illustrated in FIGS. 4-7, (without the bioresorbableexterior extrusions) are generally well-known in the art and may bemanufactured according to well-known methods. The bioresorbable exteriorextrusions may be added to the removable stents after the body of theremovable stent is constructed or may be manufactured as part of theremovable stent body. Any of the removable stents according to theembodiments of FIGS. 1-7 may be made using biostable material such asElgiloy® or Phynox® metal spring alloys, 316 stainless steel, MP35Nalloy, superelastic Nitinol nickel-titanium or similar non-bioresorbablematerials.

[0030] Referring again to the preferred embodiment of FIGS. 1 through 3,removable stent 101 is a tubular device formed from two sets ofoppositely-directed, parallel, spaced-apart and helically woundelongated strands or filaments 102. The removable stent body of FIGS. 1and 2 is described in more detail in U.S. patent application Ser. No.08/904,967, filed Aug. 1, 1997. In particular, the sets of filaments 102are interwoven in an over and under braided configuration intersectingat points such as 103 to form an open mesh or weave construction.Methods for fabricating the body of removable stents 101 are generallyknown and disclosed, for example, in the Wallsten U.S. Pat. No.4,655,771 and the Wallsten, et al. U.S. Pat. No. 5,061,275.

[0031] Removable stent 101 is shown in its expanded or relaxed state inFIGS. 1 and 2, i.e., in the configuration it assumes when subject to noexternal loads or stresses. The filaments 102 are resilient, permittingthe radial compression of removable stent 101 into a reduced-radius,extended-length configuration or state suitable for delivery to thedesired placement or treatment site through a body vessel (i.e.,transluminally). Removable stent 101 may also be self-expandable fromthe compressed state, and axially flexible. Bioresorbable exteriorextrusions 104 are also resilient permitting bioresorbable exteriorextrusions 104 to be contained within a delivery device when removablestent 101 is in a compressed state but expanded to the relaxed state asshown in FIGS. 1 and 2. Bioresorbable exterior extrusions 104 are alsoinflexible enough, so that when in the expanded state in a body lumen,bioresorbable exterior extrusions 104 prevent migration of removablestent 101 within body lumen. According to one embodiment of theinvention, at least one and preferably all bioresorbable extrusions iscomposed of one or more commercially available grades of polylactide,poly-L-lactide (PLLA), poly-D-lactide (PDLA), polyglycolide (PGA),polydioxanone, polycaprolactone, polygluconate, polylacticacid-polyethylene oxide copolymers, modified cellulose, collagen,poly(hydroxybutyrate), polyanhydride, polyphosphoester, poly(aminoacids), poly(alpha-hydroxy acid) or related copolymers materials.

[0032] According to one embodiment of the invention, removable stent 101may be a radially and axially flexible tubular body having apredetermined diameter that is variable under axial movement of the endsof the body relative to each other. Removable stent 101 may be composedof a plurality of individually rigid but flexible and elastic threadelements or filaments 102, each of which may extend in a helixconfiguration along a longitudinal center line of the body as a commonaxis. The filaments 102 may define a radially self-expanding body. Thebody may be provided by a first number of filaments 102 having a commondirection of winding but axially displaced relative to each other, andcrossing a second number of filaments 102 also axially displacedrelative to each other but having an opposite direction of winding.Bioresorbable exterior extrusions 104 are flexible in the axiallydirection of removable stent 101, but rigid in the longitudinaldirection. The flexibility of bioresorbable exterior extrusions 104 inthe axial direction allows removable stent 101, including bioresorbableexterior extrusions 104 to be compressed into a delivery device. Therigidity of bioresorbable exterior extrusions 104 in the longitudinaldirection of removable stent 101 ensures that, once removable stent 101is positioned in a body lumen, bioresorbable exterior extrusions 104will resist migration of removable stent 101 within the body lumen.

[0033] Bioresorbable exterior extrusions 104 may take a variety ofshapes. Bioresorbable exterior extrusions 104 of FIG. 1 are in the shapeof a barb with the concave surface of the barb towards the center ofremovable stent 101. Alternatively, bioresorbable exterior extrusions201 of FIG. 2 may be triangular in shape and rigid in the longitudinaldirection of removable stent 202 to resist migration in a longitudinaldirection once removable stent 202 is positioned within a body lumen.

[0034] Removable stent 301 of FIG. 3 includes a plurality ofindividually rigid but flexible and elastic thread elements or filaments302, each of which may extend in a helix configuration along alongitudinal center line of the body as a common axis. The filaments 302may define a radially self-expanding body. The body may be provided by afirst number of filaments 302 having a common direction of winding butaxially displaced relative to each other, and crossing a second numberof filaments 305 also axially displaced relative to each other buthaving an opposite direction of winding. Bioresorbable exteriorextrusions 304 are flexible in the axially direction of removable stent301, but rigid in the longitudinal direction. The flexibility ofbioresorbable exterior extrusions 304 in the axial direction allowsremovable stent 301, including bioresorbable exterior extrusions 304 tobe compressed into a delivery device. Filaments 302 and filaments 305may be configured to alternate at intersections. For example, at oneintersection filament 302 may be exterior to filament 305 as shown at303. Alternatively, filament 305 may be exterior to filament 302 atother intersections as shown at 306. FIG. 3 also shows that a number ofbioresorbable exterior extrusions may be included in an embodiment tofurther resist migration of removable stent 301 when placed within abody lumen.

[0035]FIGS. 3 through 7 show other embodiments of the placement ofbioresorbable exterior extrusions on various removable stentconfigurations. Notably, FIG. 5 depicts bioresorbable exteriorextrusions 502 along an outer circumference of removable stent 501. Notethat many orientations and configurations of bioresorbable exteriorextrusions may be configured to resist migration of the stent within abody lumen.

[0036] Note also that bioresorbable exterior extrusions of the presentinvention may be used to resist migration of other types of removablestents. Other stent structures and features may be include, for example,stents having features which enhance or cooperate with the tubular andself-expandable structure or which facilitate the implantation of thestructure. One example is the inclusion of radiopaque markers on thestructure which are used to visualize the position of the stent throughfluoroscopy during implantation. Other examples include collapsingthreads or other structures to facilitate repositioning of the stent.

[0037] Note that the use of bioresorbable exterior extrusions on aremovable stent would help ensure the proper position of the removablestent during its in service, or in the lumen, time. By selection of theproper bioresorbable materials, when the time to remove the removablestent has arrived, the bioresorbable exterior extrusions have beenabsorbed into, or broken down by the body, allowing for easy removal.

[0038] Note also that a non-bioresorbable exterior extrusion attached tothe removable stent body with bioabsorbable material may also be used inthe implementation of the present invention.

[0039]FIGS. 8 through 10 are illustrations of a delivery device 801 fordelivering removable stent 101 to a treatment site in a body vessel. Asshown, removable stent 101 is carried by the distal portion 809 ofdelivery device 801, and is placed on the delivery device in a radiallycontracted or compressed state. The proximal portion of delivery device801 generally remains outside of the body for manipulation by theoperator.

[0040] Delivery device 801 includes an elongated, inner tube 802,preferably having an axially extending lumen therethrough. The distalportion 809 of inner tube 801 is flexible and can be made from nylon orother suitably flexible biocompatible polymeric material. At its distalend, inner tube 801 is provided with a head 805. Head 805 serves tofacilitate the insertion of delivery device 801 through a narrow openingin a body vessel. The proximal portion of inner tube 802 is preferablyformed from stainless steel or other suitably rigid metal alloy. Theproximal end of the distal portion of inner tube 802 is bonded to thedistal end of the proximal portion of the inner tube in any conventionalmanner such as by using a standard adhesive.

[0041] A proximal tube 804 surrounds the proximal portion of inner tube802 in coaxial fashion. Proximal tube 804 is preferably formed frompolyurethane. The proximal end of tube 804 is connected to a valve body803 having a side port 806. An extension tube 807 extends from side port806 to an opening 808. This arrangement allows fluid to be injectedthrough extension tube 807 and between proximal tube 804 and inner tube802.

[0042] A moveable hose 901 surrounds the distal portion of inner tube802. Hose 901 is rolled over itself to form a double-walled section. Theproximal end of inner wall 1001 of a double-walled section is connecteddirectly to inner tube 802. The proximal end of the outer wall 1002 ofthe double-walled section is connected to the outer surface of thedistal portion of proximal tube 804. These connections can be achievedby any conventional means such as by a standard adhesive. Thisarrangement allows hose 901 to be rolled off removable stent 101 andplaced on the distal portion of inner tube 802. By moving valve body 803in the proximal direction, outer wall 1002 of hose 901 slides proximallyover inner wall 1001. This causes inner wall 1001 to “roll back” off ofremovable stent 101. To facilitate movement of hose 901 off of removablestent 101, at least that portion of inner wall 1001 that contacts outerwall 1002 in the area where hose 901 is rolled over to form thedouble-walled section should be lubricious. The lubriciouscharacteristic can be achieved by adding a lubricious substance to thissurface of hose 901, injecting a lubricious liquid between inner wall1001 and outer wall 1002 or forming hose 901 from a naturally slipperymaterial such as Teflon coating.

[0043] At least the surfaces of inner wall 1001 and outer wall 1002 thatface each other in the double-walled section are coated with alubricious hydrophilic coating. In one embodiment the hydrophiliccoating is 2018-M material available from Hydromer Inc. of Whitehouse,N.J. Other materials that can be used are polyethylene oxide andhyaluronic acid. When wet, the hydrophilic coating becomes lubriciousand thus reduces friction between inner wall 1001 and outer wall 1002 ofthe double-walled section of hose 901 as outer wall 1002 moves pastinner wall 1001. This facilitates the removal of the double-walledsection of hose 901 from removable stent 101. Hydrophilic material maybe added to hose 901 during the assembly of delivery device 801. Toenable the hydrophilic material to adequately bond to hose 901, thematerial used to manufacture hose 901 should be matched to thehydrophilic material used. It has been found that polyurethane workswell as a material for hose 901. In particular, a blend of 65D and 75Dpolyurethane provides sufficient flexibility to allow hose 901 to rollover itself yet still be soft enough and compatible with the hydrophilicmaterial that it can be properly coated. In one embodiment, the blend isformed of 50% 65D polyurethane and 50% 75D polyurethane. During theassembly of delivery device 801, one side of hose 901 is coated with thehydrophilic material after the outer wall 1002 of the hose has beenconnected to proximal tube 804. Isopropyl alcohol is first applied toone side of hose 901 to clean the surface and remove the waxy filmresulting from the plasticizers in the polyurethane. The same side ofhose 901 is then coated with the hydrophilic material. The surface ofhose 901 should be flushed with alcohol for about thirty seconds.Similarly, the surface of hose 901 should be flushed with thehydrophilic coating for about thirty seconds. It has been found thatthis technique deposits sufficient hydrophilic material on inner wall1001 and outer wall 1002 to allow hose 901 to be rolled back withminimal friction when the hydrophilic material is wet.

[0044] After delivery device 801 has been assembled and is ready foruse, the hydrophilic coating is wetted with physiological salinesolution by injecting the solution through extension tube 807, pastproximal tube 804 and into the space between inner wall 1001 and outerwall 1002 of the double-walled section of hose 901. Excess fluid exitsfrom the hole 902 formed toward the distal end of the double-walledsection of hose 901. In this same manner, a lubricious fluid such aspolyethylene glycol can be injected into the space between inner wall1001 and outer wall 1002 of the double-walled section to provide thelubricious characteristic of hose 901 in place of adding a lubricioushydrophilic material through hose 901 as described above.

[0045] The manner by which delivery device 801 is operated to deliverremovable stent 101 to a treatment site in a body vessel or lumenincluding curved sections is illustrated in FIGS. 11-14. As shown,removable stent 101 is placed in a radially compressed state in asurrounding relationship to the outer distal end of inner tube 802.Removable stent 101 is constrained on inner tube 802 by thedouble-walled section of hose 901. It is important that removable stent101 not be confined too tightly on inner tube 802. Hose 901 should applyjust enough force to removable stent 101 to hold removable stent 101 inplace. The double-walled section of hose 901 can be removed from aroundremovable stent 101 by pulling valve body 803 and proximal tube 804 in aproximal direction. The double-walled section “rolls” off removablestent 101. No sliding movements take place between removable stent 101and inner wall 1001 which contacts removable stent 101. Along with themovement of the double-walled section in a proximal direction, thedistal end of removable stent 101 will be exposed in a radial directionto engagement against the wall of the body vessel. As the double-walledsection of hose 901 continues moving proximally, more of removable stent101 expands in a radial direction until the entire length of removablestent 101 is exposed and engages the wall of a body.

[0046] A lumen is used to enable delivery device 801 to follow a guidewire (not shown) previously inserted percutaneously into the bodyvessel. The lumen of inner tube 802 can also be used to introduce acontrast fluid to the area around the distal end of delivery device 801so the position of delivery device 801 can be detected (e.g., throughthe use fluoroscopy or X-ray techniques).

[0047] In FIG. 15 there is shown another embodiment of a delivery devicewhich may be used to position stents including the present inventionwithin a body lumen.

[0048] This assembly constitutes a flexible instrument intended tointroduce the tubular body in contracted state into for example a bloodvessel and then to expand the body when located therein. The parts ofthe instrument consist of an outer flexible tube 1501 and a concentricalso flexible inner tube 1502. At one end of the outer tube anoperational member 1503 is arranged. Another operational member 1504 isattached to the free end of inner tube 1502. In this manner the innertube 1502 is axially displaceable in relation to the outer tube 1501. Atthe other end of inner tube 1502 a piston 1505 is attached which whenmoving runs along the inner wall of outer tube 1501.

[0049] When the instrument is to be used the tubular expansible body1506 in contracted state is first placed inside tube 1501, the innertube 1502 with the piston 1505 being located in the rear part 1507 ofouter tube 1501. The starting position of piston 1505 is shown by dashedlines at 1508 in FIG. 15. In this manner part of tube 1501 is filledwith the contracted tubular body 1506 in the starting position.

[0050] During implantation the flexible tubular part of the device isinserted to the location of a blood vessel intended for implantation.Member 1504 is then moved in the direction of arrow 1509, the contractedbody 1506 being pushed out through end 1510 of tube 1501, the part ofthe tubular body 1506 leaving tube end 1510 expanding until in itsexpanded position 1511 it is brought to engagement with the interior ofvascular wall 1512. The tubular body 1506, 1511 is for sake ofsimplicity shown in FIG. 15 as two sinus-shaped lines. To the extentthat the expanded body 1506 comes into engagement with vascular wall1512 tube end 1510 is moved by moving member 1503 in the direction ofarrow 1513. The contracted body 1506 is moved by the piston 1505 pushingagainst one end of the body. Thus, the implantation takes place bysimultaneous oppositely directed movements of members 1504 and 1503, thedisplacement of member 1504 being larger than that of member 1503. Whenthe contracted body 1506 has been fully removed from the tube 1501 theexpansion is terminated and the instrument can be removed from thelocation of the operation.

[0051] The delivery system according to FIG. 15 has the great advantagethat the constructional details are quite simple and can be operatedwith high reliability. The instrument shown is also suitable forimplantation of helices with very small diameters. As an example theremay be mentioned that experiments have been performed with a tubularexpansible body consisting of crossing thread elements, the contracteddiameter of the body being only 2 mms and the expanded diameter 6 mms.It is also fully conceivable to implant expanded bodies with evensmaller diameter. The instrument according to FIG. 15 may alsoadvantageously be used for implantation of bodies in the form of graftsof a very large diameter.

[0052] In implantation of long bodies it is conceivable that theresistance in displacing same in tube 1501 becomes too high. In thiscase it may be suitable to replace piston 1505 at the front end of tube1502 with movable jaws or latches which operate in such a manner thatwhen tube 1502 is brought forward in the direction of arrow 1509 thelatches engage the inner side of body 1506, the body being broughtforward. When tube 1502 is brought back in the direction of arrow 1513the latches are released. In this manner body 1506 can be movedforwardly by a pump-like motion of tube 1502.

[0053] Many embodiments of the different members shown in FIG. 15 are,of course, conceivable. Thus, it is possible for example to simplifyimplantation for the surgeon by controlling the relative motion betweenmembers 1503 and 1504 in a mechanical manner.

[0054] The stents of the present invention may be delivered byalternative methods or using alternative devices. For instance, thedevice described in Heyn et al. U.S. Pat. No. 5,201,757 may be utilized.

[0055] Although the present invention has been described with referenceto preferred embodiments, those skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the invention.

[0056] It will be evident from considerations of the foregoing that thedevices of the present invention may be constructed using a number ofmethods and materials, in a wide variety of sizes and styles for thegreater efficiency and convenience of a user.

[0057] The above described embodiments of the invention are merelydescriptive of its principles and are not to be considered limiting.Further modifications of the invention herein disclosed will occur tothose skilled in the respective arts and all such modifications aredeemed to be within the scope of the invention as defined by thefollowing claims.

1. A removable stent for providing reinforcement to a selected region ofa selected body lumen including a resilient cylindrical layer, theimprovement which comprises: at least one bioresorbable extrusionexterior from the resilient cylindrical layer for resisting migration ofthe removable stent when said removable stent is positioned in saidselected region of said selected body lumen.
 2. The removable stent ofclaim 1 wherein said extrusion is a barb.
 3. The removable stent ofclaim 1 that is radially self-expandable.
 4. The removable stent ofclaim 1 wherein said selected body is composed of a non-bioresorbablematerial.
 5. The removable stent of claim 1 wherein said removable stentand said at least one extrusion are part of a unitary design.
 6. Theremovable stent of claim 1 wherein said removable stent is a coveredstent.
 7. The removable stent of claim 1 wherein said removable stent isa ePTFE covered removable stent.
 8. The removable stent of claim 1wherein said at least one bioresorbable extrusion is composed ofmaterial selected from the group consisting of PGA, PLA, PEO, nylon andpolyester urethane.
 9. A temporary implantable endoprosthesis includinga tubular, radially compressible and axially flexible structure, theimprovement which comprises: at least one bioresorbable extrusionexterior from the resilient cylindrical layer for resisting migration ofthe stent when said stent is positioned in said selected region of saidselected body lumen.
 10. The temporary implantable endoprosthesis ofclaim 9 wherein said extrusion is a barb.
 11. The temporary implantableendoprosthesis of claim 9 that is radially self-expandable.
 12. Thetemporary implantable endoprosthesis of claim 9 wherein said temporaryimplantable endoprosthesis is made of non-bioresorbable material. 13.The temporary implantable endoprosthesis of claim 9 wherein saidremovable stent and said at least one extrusion are part of a unitarydesign.
 14. The temporary implantable endoprosthesis of claim 9 whereinsaid removable stent is a covered stent.
 15. The temporary implantableendoprosthesis of claim 9 wherein said removable stent is a ePTFEcovered removable stent.
 16. The temporary implantable endoprosthesis ofclaim 9 wherein said at least one extrusion is composed of materialselected from the group consisting of PGA, PLA, PEO, nylon and polyesterurethane.
 17. A method of reducing migration of a removable stentcomprising the steps of: constructing said removable stent including aresilient cylindrical layer; placing at least one bioresorbableextrusion exterior from the resilient cylindrical layer of saidremovable stent on said removable stent; positioning said removablestent in a body lumen; expanding said removable stent within said bodylumen; and resisting migration of said removable stent by interactionbetween said at least one bioabsorbable extrusion and said body lumen.18. The method of claim 17 wherein said step of placing at least onebioresorbable extrusion is performed when the removable stent isconstructed as a unitary removable stent.
 19. The method of claim 17wherein said step of placing at least one extrusion is performed afterthe resilient cylindrical layer of said removable stent is completed.20. The method of claim 17 wherein said step of expanding said removablestent is accomplished by including self-expanding material in theconstruction of said removable stent.
 21. The method of claim 17 whereinsaid step of resisting migration is performed by forming said at leastone extrusion in the shape of a barb.
 22. The method of claim 17 whereinsaid step of resisting migration is performed by said at least oneextrusion interacting with the wall of said body lumen.
 23. The methodof claim 17 further comprising the step of: weakening said at least oneextrusion by forming said extrusion of a bioabsorbable material.
 24. Themethod of claim 23 wherein the step of weakening said at least oneextrusion is accomplished by forming the extrusion of material selectedfrom the group consisting of PGA, PLA, PEO, nylon and polyesterurethane.